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Mars Global Surveyor
Mars Orbiter Camera

MGS MOC Image of Mars Exploration Rover, Spirit, on Mars

MGS MOC Release No. MOC2-614, 23 January 2004

MGS MOC view of MER-A (Spirit) Lander and Vicinity on 19 January 2004 (1 km by 1.3 km)
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MGS/MOC MER-A/DIMES Stereo Anaglyph of Lander and Vicinity
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Annotated MGS MOC view of MER-A (Spirit) Lander and Vicinity on 19 January 2004
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Annotated MGS/MOC MER-A/DIMES Stereo Anaglyph of Lander and Vicinity
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all images credit: NASA/JPL/Malin Space Science Systems.
The MER-A DIMES image used in these products is courtesy NASA/JPL.
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The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC), operating in martian orbit since September 1997, acquired an image of the Mars Exploration Rover (MER-A), Spirit, on 19 January 2004. The Spirit/Columbia Memorial Station is clearly seen as a bright feature in the image (above left two images, one annotated), as are the parachute and backshell from which Spirit was detached during the landing on 4 January 2004. Also evident is a dark scar on the rim of a crater to the northeast of the lander; this dark marking was not present prior to landing, and is believed to have been caused by the impact of Spirit's heatshield. The lander is white because the data received from Mars were saturated at this location--that is, the lander was so much brighter than the surrounding terrain that the camera saw it as a white object.

The MGS MOC image was combined with the third MER-A descent image (DIMES #3; DIMES = Descent Image Motion Estimation System) to make a stereo anaglyph (right, two images, one annotated; 3-d red/blue glasses necessary for stereo effect) of the landing site. The DIMES image was acquired at an altitude of about 1.4 km (~0.9 mi) above the surface on 4 January as Spirit was descending. The DIMES image shows the heatshield (see annotated views, above) as it was falling away from the lander; this shows up in the 3-d picture as a dark blue/black feature. The DIMES image also showed the shadow of Spirit's open parachute as it was descending (see annotated views above). The heatshield in the DIMES image was in the air, approximately 600 m (~1970 ft) away from the lander. Neither the parachute shadow nor the heatshield are seen in the MOC image acquired 19 January. However, features related to the lander that were not in the DIMES image but appear in the MOC view include: the lander, the backshell and parachute, the impact scar made by the heatshield after it hit the ground, and some of the initial bounce marks made by Spirit's airbags.

The MOC image of the Spirit lander and its landing site was acquired using a new technique that was pioneered by the MGS project in 2003. Called "cPROTO" (for Pitch and Roll Only Targeted Observation with planetary motion compensation), the approach allows MOC, which normally takes pictures 1.5 meters (5 feet) per pixel to 12 meters (40 feet) per pixel, to acquire images with a higher resolution. By pitching the MGS spacecraft at a rate faster than it orbits around Mars, and moving it in a way that compensates for the rotation of the planet, MOC is able to obtain images with a down-track resolution of about 50 cm/pixel (~20 inches/pixel), although the cross-track resolution remains ~1.5 m/pixel (5 ft/pixel). These images have a better signal-to-noise ratio than typical 1.5 m/pixel MOC images, as well. This technique allows the lander and other details not normally visible in a full-resolution MOC image to be seen. After Spirit landed, the MGS MOC team made two attempts to image the lander using the cPROTO method. The technique is still so new that it's quite challenging to hit a target on the first try. Thus, the first attempt, on 10 January 2004, missed the lander by about 150 meters (~490 ft). The second attempt, on 19 January 2004, got the lander and other features. The two January 2004 cPROTO images have been mosaiced together (bottom picture, above) to provide a nice overview of the landing site. The light-toned features on the far right of the mosaic are the hills seen to the southeast of the lander in Spirit's early January panorama.

Each image shown here is located in Gusev Crater near 14.7°S, 184.6°W. North is up and sunlight illuminates each image from the left. The MOC images were acquired near 2 p.m. local time on Mars. The lander appears white because the DNs (data numbers) received from Mars for the lander were 255--the maximum possible (i.e., the lander was saturated). The values were saturated because of the high sun elevation angle and the fact that the lander and parachute are covered with highly reflective, light-toned materials (as seen in the lander portrait released on 21 January 2004). In the annotated pictures, the "DIMES 'First Bounce' Estimate" is the preliminary location where Spirit's airbags were believed to have first hit the surface (a revised location was expected to be reported at the Spirit press briefing on Friday, 23 January 2004). The "Surface Feature Localization" is the location of the lander that was estimated by the MER-A team using sight lines to landmarks in the lander's panoramic images. The MOC image shows that the estimation by sightlines was good to better than 20 meters (~65 ft). Note that the heatshield and parachute shadow are not visible in the annotated MOC image, but appear in the stereo view made by combining the DIMES and MOC images; also note the dark feature on the crater rim (heatshield impact location), the airbag bounce marks, and the bright features (lander, parachute, backshell) were visible to MOC but not present on the surface when the DIMES image was acquired.

Other MGS MOC Images of MER-A, Spirit, Landing Site:

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Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, California. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, California and Denver, Colorado.

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